1. Field of the Invention
The present invention is directed to a slit valve that enables two-way fluid flow, and in particular a slit valve for use with implantable, inflatable medical devices such as gastric balloons for the treatment of obesity.
2. Description of the Related Art
There are a wide variety of known inflatable devices that can be implanted in the body. One such inflatable implantable medical device is a gastric balloon, as described in U.S. Pat. No. 5,084,061, or commercially available as the BioEnterics Intragastric Balloon System (sold under the trademark BIB®). These devices are designed to provide therapy for moderately obese individuals who need to shed pounds in preparation for surgery, or as part of a dietary or behavioral modification program.
The BIB System, for example, consists of a silicone elastomer gastric balloon that is inserted into the stomach and filled with fluid. Commercially available gastric balloons are filled with saline solution or air. The gastric balloon functions by filling the stomach and enhancing appetite control. Placement of the gastric balloon is non-surgical, usually requiring no more than 20-30 minutes. The procedure is performed endoscopically in an outpatient setting, using local anesthesia and sedation. Placement is temporary, and gastric balloons are typically removed after six to twelve months.
There are known in the prior art a variety of valves for use with such gastric balloons. For example, the valve described in U.S. Pat. No. 5,084,061, shown in FIG. 1, consists essentially of a leaf valve (also known as a duckbill valve) comprising two relatively flat pieces of silicone elastomer bonded along their longitudinal edges and affixed by adhesive to the end of the valve stem. In operation, a filler tube, which is usually a plastic or silicone tube containing a stainless steel stiffening rod, is inserted through an X-shaped slot, through a hole, through a tubular valve stem, through a second X-shaped slot in the membrane, and through the leaf valve until the filler tube itself is in the interior of the shell. In such a position, both addition and withdrawal of fluid can be accomplished. For addition of fluid only, the filler tube does not need to penetrate through the leaf valve.
However, valves of this sort have several disadvantages. Initially, these valves are prone to leaking One way in which a duckbill valve may develop leaks is through the initial filling of the balloon when one of the flat pieces of elastomer becomes kinked or develops a curvature through which the fluid can pass. Another way is through the fluid removal process, which requires the insertion of the filler tube completely through the valve and into the interior of the shell. Following removal of a portion of the fluid and the filler tube, the leaf valve can remain partially open. This causes even greater amounts of the fluid to be released from the implant. Accordingly, there is a need for a valve that does not leak following either filling or removal of fluid from the shell.
Second, the prior art leaf valves face opposing problems in that it is necessary to reduce the pressure necessary to insert the filler tube into the valve to ease in installation and filling, but if there is not a sufficiently tight fit between the filler tube and the valve, then the pressure of the fluid in the balloon or valve may force the filler tip out of the valve before filing is complete. Further, it is necessary to consider the amount of force necessary to remove the fill tube from the valve. Current designs, such as that discussed above, often require too much pressure to insert the filler tube into the valve and too much pressure to remove the filler tube from the valve. Alternatively, in instances where the pressure necessary to insert and remove the filler tube are not great, the filler tube may pop out of the valve while filling the balloon. Accordingly, there is a need for a valve that promotes easy insertion and removal of the filler tube, but does not force the filler tube out of the valve while filling the balloon. Prior art leaf valves are also unsuitable at fluid inflation pressures above 30 psi, which may damage the valve.
Finally, the prior art duckbill valves have the shortcoming that they are only one-way valves. They cannot be used to direct fluid flow in both directions without inserting a tube completely through the valve. Situations arise where it is preferable to have a two-way valve. For example, when a device absorbs additional fluid through osmosis after being implanted in the body and filled to a proper volume, it may be desirable to reduce the fluid volume of that implant. In the duckbill valve described above, no amount of pressure on the interior of the balloon will permit egress of the fluid contained therein. Accordingly, there is a need to a valve that is capable, of permitting back flow of fluid (i.e., from the interior to the exterior), while generally preventing egress of fluid when under normal pressure.
Another type of valve often used in implant technology is a diaphragm valve, such as a that discussed in U.S. Pat. No. 6,419,699 assigned to McGhan Medical Corporation. The diaphragm valve requires insertion of a rigid male component on the inflation tube to open the valve and allow fluid transfer. Upon removal of the inflation tube, fluid pressure within the implant forces the valve closed and creates a leak proof seal. As with the leaf valve, such a valve does teach any means for backflow through the valve.
Other valves that are used in medical applications include a connector for an instrument insertion passage described in U.S. Pat. No. 5,599,327 (“the '327 patent”), a non-binding surgical valve as described in U.S. Pat. No. 5,916,198 (“the '198 patent”), and a needle less injection site as described in U.S. Pat. No. 6,261,268 (“the '268 patent”). Each of these valves or connectors has shortcomings that are addressed by the present invention. Initially, both the '327 and the '268 patents contemplate an opening in the valve that forms a seal with the application of mechanical pressure by a medical instrument. Accordingly, both the '327 and '268 patents require the use of bulky components and mechanical force to create a seal. Such components and use of mechanical force are not conducive for use with implant technology. Further, the '198 patent describes a one-way valve that is closed by insufflation gases acting on an interior surface of the valve via a passage in one of the valve segments. Accordingly, the valve contemplated by the '198 patent does not overcome the shortcomings of the prior art discussed above. Therefore, the present invention is directed at overcoming these problems associated with the prior art valves. The present invention is related to a two-way valve that is usable in an implantable medical device such as a gastric balloon. These and other characteristics of the present invention will become apparent from the further disclosure to be made in the detailed description given below.